The invention relates to a method for continuously determining the oil change interval for an internal combustion engine, and more specifically the invention relates to a method for continuously determining the oil change interval for an internal combustion engine where the oil change interval is based primarily on the number of engine starts and stops and time spent operating the engine at high speed.
A conventional mobile temperature control system includes a prime mover which may be an internal combustion engine such as a diesel engine. Such prime movers commonly drive refrigerant compressors which in turn pump refrigerant through the temperature control system to achieve and maintain the required temperature in a conditioned space.
It is well known that the oil lubricating the component parts of the internal combustion engines has a finite useful life and as a result, the oil must be changed before it becomes unsuitable to lubricate the engine components. If the oil is not changed before it becomes unsuitable for lubrication of the engine's component parts, the engine's useful life could be negatively affected. Conversely, changing the oil too soon before it becomes unsuitable for lubrication would result in a waste of oil. Therefore, methods have been developed to more precisely determine when lubricating oil needs to be changed.
The oil change interval is often affected by engine rotational speed which causes oil oxidation. It can be difficult to precisely determine the required oil change interval based solely on engine speed because the engine speed is typically variable during operation of the temperature control system and moreover, it is difficult to predict the engine speed because the engine speed varies according to a plurality of factors including: the characteristics of the load in the cargo space being conditioned by the temperature control system, the set point temperature of the conditioned space, the ambient temperature, and the frequency of the openings of the conditioned space access door during cargo transfers.
Prior art inventions have addressed determining the required oil change interval based on engine speed. For example, U.S. Pat. No. 5,530,647 issued assigned to Thermo King Corporation discloses a method for dynamically determining the oil change interval for an internal combustion engine by accumulating operating time for an internal combustion engine operating at high and low engine speeds; and after summing the accumulated operating information, determining if the engine has reached a predetermined operating level. If the engine has reached the predetermined operating level, the operator is informed that the oil needs to be changed.
Other prior art inventions relate to systems and methods for determining the oil change interval based on the level of undissolved particulate matter in the oil. U.S. Pat. No. 4,506,337 issued assigned to Nissan Motor Company; and U.S. Pat. No. 5,750,887 issued assigned to Caterpillar Incorporated disclose methods for determining when engine oil needs to be changed by determining if the amount of undisolvable soot or particulate matter in the oil exceeds a predetermined level.
Known prior art temperature control systems and methods do not calculate the oil change interval based on the number of engine starts and stops. Engine starts and stops increase the oil carbon content through "carbon loading". During starting and stopping of the engine increased amounts of carbon are introduced in the engine oil. Carbon-containing blow by combustion gas that leaks past the rings to the engine block makes contact with oil, and mixes with the oil, and in this way, carbon loads the oil. Increased carbon content in the oil shortens the requisite oil change interval. It would be beneficial to calculate the oil change interval based on starting and stopping the engine to consider the effects of carbon loading on the oil change interval.
The foregoing illustrates limitations known to exist in present devices and methods. Thus, it is apparent that it would be advantageous to provide an alternative method directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative method is provided including features more fully disclosed hereinafter.